粗体和下划线下拉列表菜单项asp.net

我有个问题要问。我的应用程序中有一个下拉列表。但是，下拉列表采用层次结构格式填充。请把这张照片剪下来

如上图所示。如何在父菜单项（如男士、女士和NA上加粗和下划线另一方面，父菜单项也不允许选择

这是我的代码

        private void createDDLCategory()
    {
        ddlCategory.AppendDataBoundItems = true;
        ddlCategory.Items.Insert(0, new ListItem("All","A"));
        ddlCategory.SelectedIndex = 0;



        var ddl1 = dropdownlist.ddlCategoryWithoutGroup();
        foreach (var value in ddl1)
        {
            if (value.P_CATEGORY_ID == null)
            {

                this.ddlCategory.Items.Add(new ListItem(value.CATEGORY_NAME, value.CATEGORY_ID.ToString()));
                this.ddlCategory.Items.FindByValue(value.CATEGORY_ID.ToString()).Selected = false;

                this.ddlCategory.Items.FindByValue(value.CATEGORY_ID.ToString()).Attributes.Add("disabled", "true");
                this.ddlCategory.Items.FindByValue(value.CATEGORY_ID.ToString()).Attributes.Add("style", "font-weight:bold;");

                foreach (var valueChild in ddl1)
                {

                    if (valueChild.P_CATEGORY_ID == value.CATEGORY_ID)
                        this.ddlCategory.Items.Add(new ListItem("   " + valueChild.CATEGORY_NAME, valueChild.CATEGORY_ID.ToString()));
                }
            }
        }


        foreach (ListItem item in ddlCategory.Items)
        {
            item.Text = HttpUtility.HtmlDecode(item.Text);

        }



    }

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感谢您的帮助。谢谢您是否尝试过以下方法：

ddlCategory.Items.FindByValue("0").Attributes.Add("style", "font-weight:bolder")

MSDN提到只有少数样式属性适用于IE